The present invention relates to wellbore tools and more particularly to a magnetic tool for retrieval of metal objects, such as cuttings and other foreign objects that accumulate in the process of perforating or milling over bridge plugs and other down hole obstructions from a wellbore.
As the conventional petroleum resources are becoming more difficult to access, the industry started developing means for drilling in more difficult strata, often in high-pressure or less stable environments. A new technique called coiled tubing drilling has been used in places where air drilling, mud drilling or fluid drilling are impracticable. Instead of conventional vertical drill string, the coil tubing method uses a continuous string of concentric coil tubing, which allows fluid circulation through the tubing. Coil tubing drilling is believed to reduce formation damage as it allows for drilling with less contact between a drill string and the surrounding formation. An additional advantage of coiled tubing method is related to continuous circulation while drilling, which is believed to minimize pressure fluctuations and reduces formation damage.
However, similar to conventional technique, coiled tubing method generates metal cuttings, or shavings, which have to be removed to stimulate fluid circulation. The present invention contemplates provision of a magnetic tool for retrieval of metal objects from a well bore when using coil tubing drilling method.